1. Field
The present disclosure of invention relates to a thin film transistor. More particularly, exemplary embodiments relate to a thin film transistor including a semiconductive oxide, a display substrate having the thin film transistor and a method of manufacturing the thin film transistor
2. Description of Related Technology
Generally, a thin film transistor (TFT) as used for example for driving a corresponding pixel unit in a display device includes a gate electrode, a source electrode, a drain electrode, and a channel layer forming a channel between the source electrode and the drain electrode. The channel layer includes a semiconductive layer (active layer) including amorphous silicon, polycrystalline silicon, semiconductive oxide, or the like.
Amorphous silicon has a relatively low electron mobility, which may be about 1 to about 10 cm2/V, so that a thin film transistor including amorphous silicon has relatively low driving characteristics. In contrast, polycrystalline silicon has a relatively high electron mobility, which may be about 10 to about hundreds cm2/V. However, a crystallization process is required for forming polycrystalline silicon at each location across the area of a substrate where the TFTs are formed. Thus, it is difficult to form a uniform polycrystalline silicon layer on a large-sized substrate (for example one used for large sized televisions), and resulting manufacturing costs are high. Semiconductive oxides may be formed through a low-temperature process, and may be easily large-scaled, and have a high electron mobility. Thus, research is actively being conducted on thin film transistors which include a semiconductive oxide in place of more traditional semiconductors.
For manufacturing a display substrate including a semiconductive oxide, a method using a photoresist pattern having a thickness gradient for a half-tone exposure is known and used.
However, when a semiconductive oxide pattern is formed by the method the photoresist pattern having a thickness grade, the semiconductive oxide pattern tends to protrude beyond an end of a source metal pattern in a lateral direction where the protruding part can define an excessive parasitic capacitance, where the latter may cause degradation of image quality such as creation of a waterfall effect.
It is to be understood that this background of the technology section is intended to provide useful background for understanding the here disclosed technology and as such, the technology background section may include ideas, concepts or recognitions that were not part of what was known or appreciated by those skilled in the pertinent art prior to corresponding invention dates of subject matter disclosed herein.